Record disk for graphophones and method of forming same



H. PAKEMAN.

RECORD DISK FUR GRAPHOPHONES AND METHOD OF FORMING SAME. APPLICATION FILED MAY 10. I921.

1,409,568. Patented Mar. 14, 1922.

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- HARRY PAKEMAN, OF CAMDEN, NEW JERSEY.

RECORD msx roR enunornouns AND METHOD or FORMING SAME a ncauon meem 10,

To aZZ whom it may concern Be it known that I. HARRY PAKEMAN, a

. greater efi'ectiveness .in so far as various features of sound reproduction are concerned than results from the usual constnuction of record. disks now on the market, may be obtained. In the manufacture of disks for graphophones at the present time, stamping is universally resorted to, the material at the time of stamping being in plastic doughlike form which is baked and cooled in such manner that the sound grooves are rendered permanent. It is also quite common to finish the record disks with plain rim bands around the outer edge of the sound groove which bands on account of the natural contraction of the material in cooling, create a pressure around the outer portion of the sound groove which pressure is of course constant thereafter and materially detracts from efiiclient reproduction to such an extent that in many song pieces the words are obscured and in many pieces involving a number of instruments it is exceedingly difficult to distinguish one instrument from the other.

It is the aim of my invention to avoid the above disadvantages by subsequently removing the rim band of the disk after the latter has hardened, the pressure on the sound groove being eliminated in this way and I have found by so doing efficiency in reproduction is materially increased and in fact increased to such an extent that ordinarily obscure words in a song piece become plain and one instrument may be readily distinguished from another in an instrumental piece involving a niunber of instruments ordinarily difiicult to distinguish between.

In the accompanying drawing which forms a part of this specification,

Figure 1 is a face view of a record disk as ordinarily constructed and finished,

Figure 2 is a similar view of the record Specification of Letters Patent.

Patented Mar. 14, 1922. 1821. Serial No. 468,212.

disk in which the rim is removed along a concentric line to relieve pressure on the sound groove, and

Figure 3 is a face view of a disk havin a recessed or scalloped edge the effect of which is to relieve pressure on the sound groove.

In Figure 1 the ordinary record disk 10 is shown in its finished form with a sound groove 11 and a plain rim band 12 around the outer edge of the sound groove which in the usual method of forming the disk contracts during cooling of the plate after stamping and baking, the contraction of this rim band creating pressure around and against the sound groove portion of the plate or disk, which pressure is of course constant.

y invention proposes a method wherein the disk or plate is formed as usual by stamping, baking and cooling, band just as shown in Figure 1, but adds to the usual method a subsequent operation in which this rim band is treated so as .to reheve the pressure on the sound groove caused by its contraction during coolin the last mentioned or finishing step of t e method taking place after the disk with its rim band has cooled and hardened in the permanent form.

This relief or pressure may be accomplished by removing the rim band along a line concentric with the disk more or less closely adjacent to the outer edge of the sound groove as I have shown in Figure 2 in connection with the disk 10 the sound groove of which is indicated at 11*.

It is not necessary however to wholly remove the rim band and as it is possible retention of a portion thereof may be important for protective purposes, I may simply recess the rim band around the edge of the disk as shown in Figure 3 in connection with the disk 10, the sound groove of which appears art 11 and the rim band of which is shown recessed or scalloped at 12, the recessing or scalloping being accomplished after the disk has cooled and hardened.

Either of the above forms of construction may be carried out at the time of manufacture of the disk or at any time subsequent thereto and it is obvious therefore that the advantages arising from the invention may be secured both in connection with. new records and those already in use.

I claim:

l. A record disk having a record portion with a rim and acompressed marginal rim, a portion with a rim band around its sound groove, of the latter being cut away whereby to repermitting the disk to cool and harden, and lieve tension on the record portion. then cutting the rim band away suflicient to 10 2. A record disk including a sound groove relieve pressure caused by its contraction 5 and having a scalloped surrounding edge. during cooling and hardening.

3. The herein described method which con'sists in stamping a record disk as usual HARRY PAKEMAN. 

